Low surface energy substrates such as polyethylene, polypropylene, and other polyolefins are characterized as having critical surface tensions of wetting of about 35 dynes/cm or less. Such surfaces are generally unreceptive to inks, paints, and adhesives due to their poor wettability. There is a need to improve adhesion to such surfaces, as well as to high energy surfaces.
Some tapes afford very high bond strengths to a wide variety of clean substrates. In some instances, primers may be applied before bonding to ensure maximum bond strength, which can be desirable for some applications. Use of some conventional primers may be complicated by various factors, including government regulations and detrimental effects to substrates, such as for example, crazing and corrosion.
Commercially available primers, such as those known as universal primers, advertise adhesion to low surface energy, medium surface energy, and high surface energy substrates including polypropylene, thermoplastic polyolefin, ABS, Nylon, acrylic, polycarbonate, paints, stainless steel, and aluminum. These primers often comprise aromatic solvents (e.g. xylene, toluene, ethylbenzene, chlorobenzene), halogen-based compounds (e.g. chlorinated polyolefin), and Bisphenol A-based compounds (e.g. epoxy resin).
There is a need for primer compositions comprising a primer component that provide strong adhesion to a wide range of low surface energy, medium surface energy, and high surface energy surfaces that are substantially free of aromatic solvents, halogen compounds, and Bisphenol A-based compounds. There is also a need for these primer compositions to provide strong adhesion between double sided tapes, such as for example, double sided foam tapes, and a wide range of surfaces.